Launching Gentoo VMs on okeanos.io

October 23, 2012

For about a year now, I’ve been working at GRNET on its (OpenStack API compliant) open source IaaS cloud platform Synnefo, which powers the ~okeanos service.

Since ~okeanos is mainly aimed towards the Greek academic community (and thus has restrictions on who can use the service), we set up a ‘playground’ ‘bleeding-edge’ installation (okeanos.io) of Synnefo, where anyone can get a free trial account, experiment with the the Web UI, and have fun scripting with the kamaki API client. So, you get to try the latest features of Synnefo, while we get valuable feedback. Sounds like a fair deal. :)

Unfortunately, being the only one in our team that actually uses Gentoo Linux, up until recently Gentoo VMs were not available. So, a couple of days ago I decided it was about time to get a serious distro running on ~okeanos (the load of our servers had been ridiculously low after all :P). For future reference, and in case anyone wants to upload their own image on okeanos.io or ~okeanos, I’ll briefly describe the steps I followed.

4) Chroot and install Gentoo in /mnt/gentoo. Just follow the handbook. At a minimum you’ll need to extract the base system and portage, and set up some basic configs, like networking. It’s up to you how much you want to customize the image. For the Linux Kernel, I just copied directly the Debian /boot/[vmlinuz|initrd|System.map] and /lib/modules/ of the VM (and it worked! :)).

and make sure you have a sane grub.cfg (I’d suggest replacing all references to UUIDs in grub.cfg and /etc/fstab to /dev/vda[1]).
Now, outside the chroot, run:
grub-install --root-directory=/mnt --grub-mkdevicemap=/mnt/boot/grub/device.map /dev/loop0

snf-image-creator takes a diskdump as input, launches a helper VM, cleans up the diskdump / image (cleanup of sensitive data etc), and optionally uploads and registers our image with ~okeanos.

For more information on how snf-image-creator and Synnefo image registry works, visit the relevant docs [1][2][3].

0) Since snf-image-creator will use qemu/kvm to spawn a helper VM, and we’re inside a VM, let’s make sure that nested virtualization (OSDI ’10 Best Paper award btw :)) works.

First, we need to make sure that kvm_[amd|intel] is modprobe’d on the host machine / hypervisor with the nested = 1 parameter, and that the vcpu, that qemu/kvm creates, thinks that it has ‘virtual’ virtualization extensions (that’s actually our responsibility, and it’s enabled on the okeanos.io servers).

If everything goes as planned, after snf-image-creator terminates, you should be able to see your newly uploaded image in https://pithos.okeanos.io, inside the Images container. You should also be able to choose your image to create a new VM (either via the Web UI, or using the kamaki client).

That’s all for now. Hopefully, I’ll return soon with another more detailed post on scripting with kamaki (vkoukis has a nice script using kamaki python lib to create from scratch a small MPI cluster on ~okeanos :)).